Skinning of ceramic honeycomb bodies

ABSTRACT

A ceramic honeycomb body having a skin that does not block partial cells extending from an inlet face to an outlet face at an outer periphery portion of the body. A method of making the ceramic honeycomb body having the skin includes disposing a sheet on an outer peripheral wall of a honeycomb core having an outer surface spaced apart from interiors of the partial cells and skinning the body having the sheet disposed thereon. Subsequent curing in the method bonds the skin to cell walls of the body spaced apart from interiors of the partial cells.

BACKGROUND

Field

Exemplary embodiments of the present disclosure relate to skinning ofhoneycomb bodies and, more particularly, to skinned honeycomb bodieshaving open peripheral partial cells and methods of manufacturing thesame.

Discussion of the Background

After-treatment of exhaust gas from internal combustion engines may usecatalysts supported on high-surface area substrates and, in the case ofdiesel engines and some gasoline direct injection engines, a catalyzedfilter for the removal of carbon soot particles. Filters and catalystsupports in these applications may be refractory, thermal shockresistant, stable under a range of pO₂ conditions, non-reactive with thecatalyst system, and offer low resistance to exhaust gas flow. Porousceramic flow-through honeycomb substrates and wall-flow honeycombfilters (generically referred to herein as honeycomb bodies) may be usedin these applications.

Particulate filters and substrates may be difficult to manufacture toexternal dimensional requirements set by original equipmentmanufacturers (OEMs) and the supply chain due to drying and firingshrinkage during manufacturing. Consequently, ceramic cement may be usedto form an exterior skin of a honeycomb body which has been machined or“contoured” to a desired dimension. As used herein, the term “honeycombbody” includes single honeycomb monoliths and honeycomb bodies formed bymultiple honeycomb segments that are secured together, such as by usinga ceramic cement to form a monolith. Ceramic cement may be mixed andapplied to a fired, contoured or segmented honeycomb body and the wetskin allowed to dry. The act or process of applying ceramic cement tothe exterior of the honeycomb body is referred to herein as “skinning”the honeycomb body. A honeycomb body having skin disposed thereon isreferred to herein as a “skinned” honeycomb body. As disclosed herein,contouring refers to grinding, machining, cutting, drilling, coredrilling, etc. to a desired dimension.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure andtherefore it may contain information that does not form any part of theprior art nor what the prior art may suggest to a person of ordinaryskill in the art.

SUMMARY

Exemplary embodiments of the present disclosure provide skinnedhoneycomb bodies having open partial channels extending from an inletface to an outlet face at an outer peripheral portion.

Exemplary embodiments of the present disclosure also provide a method ofmanufacturing the skinned honeycomb bodies having open partial cellchannels extending from an inlet face to an outlet face at an outerperipheral portion.

Additional features of the disclosure will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the disclosure.

An exemplary embodiment discloses a honeycomb body. The body includes ahoneycomb core having a plurality of channel walls extending from aninlet face to an outlet face defining cell channels therebetween, anouter periphery extending from the inlet face to the outlet face, andpartial cell channels adjoining the outer periphery of the honeycombcore, wherein channel walls of each partial channel comprise a gap atthe outer periphery of the honeycomb core and each partial cell channelcomprises a volume from the inlet face to the outlet face being enclosedby the channel walls and the gap at the honeycomb core periphery. Theceramic article includes a skin disposed on the outer periphery of thehoneycomb core across the gaps such that a majority of the total partialcell channel volume is open from the inlet face to the outlet face.

An exemplary embodiment also discloses a method of manufacturing ahoneycomb body. The method includes disposing a sheet on an outerperipheral surface of a honeycomb core, wherein the outer peripheralsurface extends from a first end face to a second end face of thehoneycomb core, disposing skin batch on the sheet, and curing the skinbatch to bond the cured skin to the honeycomb core to form the honeycombbody. In the method, curing comprises sacrificing at least a portion ofthe sheet and the cured skin forms an outer wall of a portion ofperipheral partial cell channels open from the first end face to thesecond end face.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the disclosure.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thedisclosure, and together with the description serve to explain theprinciples of the disclosure.

FIG. 1A shows a schematic perspective view of a honeycomb bodycomprising a skin on an outer periphery of a honeycomb core not fillingpartial cells thereof according to exemplary embodiments of thedisclosure. FIG. 1B is a schematic cross section through the honeycombbody of FIG. 1A according to these exemplary embodiments of thedisclosure. FIG. 1C is a schematic top view of the honeycomb body ofFIG. 1A according to these exemplary embodiments of the disclosure.

FIG. 2 shows a schematic perspective view of a honeycomb core comprisingpartial cells on an outer periphery thereof in a method according toexemplary embodiments of the disclosure.

FIG. 3A shows an end view of the honeycomb core comprising partial cellson an outer periphery thereof shown in FIG. 2 having a sheet disposed onthe outer periphery in a method according to these exemplary embodimentsof the disclosure. FIG. 3B shows an end view of the honeycomb corecomprising partial cells on an outer periphery thereof shown in FIG. 3Ahaving a skin batch disposed on the sheet disposed on the outerperiphery in a method according to these exemplary embodiments of thedisclosure. FIG. 3C shows an end view of the honeycomb core comprisingpartial cells on an outer periphery thereof shown in FIG. 2 having askin batch disposed on a filling material disposed on the outerperiphery in a method according to these exemplary embodiments of thedisclosure.

FIG. 4 presents a photograph of a honeycomb core comprising partialcells on an outer periphery thereof in a method according to theseexemplary embodiments of the disclosure.

FIG. 5 presents a photograph of a honeycomb body comprising partialcells on an outer periphery thereof filled with skinning materialaccording to a comparative example.

FIG. 6A is a photograph of the honeycomb core comprising partial cellson an outer periphery thereof having a sheet disposed on the outerperiphery in a method according to these exemplary embodiments of thedisclosure. FIG. 6B is a photograph of the honeycomb core comprisingpartial cells on an outer periphery thereof having a coarse weave sheetdisposed on the outer periphery in a method according to these exemplaryembodiments of the disclosure. FIG. 6C is a photograph of the honeycombbody of FIG. 6B comprising an applied skin cement material on top ofwrapped coarse weave sheet and after drying at 100° C. for 120 minutesnot filling partial cells thereof according to exemplary embodiments ofthe disclosure. FIG. 6D is a photograph of the honeycomb body of FIG. 6Acomprising an applied skin cement material on top of wrapped sheet andafter drying at 100° C. for 120 minutes not filling partial cellsthereof after firing at 550° C. for 60 minutes according to exemplaryembodiments of the disclosure.

FIG. 7A is a photograph of a honeycomb body comprising a skin on anouter periphery not filling partial cells thereof according to exemplaryembodiments of the disclosure. FIG. 7B is a higher magnificationphotograph of a honeycomb body comprising a skin on an outer peripherynot filling partial cells shown in FIG. 7A.

FIG. 8 is a photograph of sheets of various composition, mesh size, andthicknesses according to exemplary embodiments of the disclosure used inskinning methods according to exemplary embodiments of the disclosure.

DETAILED DESCRIPTION

The disclosure is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the disclosureare shown. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure is thorough, and will fully convey the scope of thedisclosure to those skilled in the art. In the drawings, the size andrelative sizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to”, or “adjacent to” another element or layer,it can be directly on, directly connected to, or directly adjacent tothe other element or layer, or intervening elements or layers may bepresent. In contrast, when an element or layer is referred to as being“directly on”, “directly connected to”, or “directly adjacent to”another element or layer, there are no intervening elements or layerspresent. Like reference numerals in the drawings denote like elements.It will be understood that for the purposes of this disclosure, “atleast one of X, Y, and Z” can be construed as X only, Y only, Z only, orany combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ,ZZ).

In these exemplary embodiments, the disclosed article, and the disclosedmethod of making the article provide one or more advantageous featuresor aspects, including for example as discussed below. Features oraspects recited in any of the claims are generally applicable to allfacets of the disclosure. Any recited single or multiple feature oraspect in any one claim can be combined or permuted with any otherrecited feature or aspect in any other claim or claims.

While terms such as, top, bottom, side, upper, lower, vertical, andhorizontal are used, the disclosure is not so limited to these exemplaryembodiments. Instead, spatially relative terms, such as “top”, “bottom”,“horizontal”, “vertical”, “side”, “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

“Include,” “includes,” or like terms means encompassing but not limitedto, that is, inclusive and not exclusive.

“About” modifying, for example, the quantity of an ingredient in acomposition, concentrations, volumes, process temperature, process time,yields, flow rates, pressures, viscosities, and like values, and rangesthereof, employed in describing the embodiments of the disclosure,refers to variation in the numerical quantity that can occur, forexample: through typical measuring and handling procedures used forpreparing materials, compositions, composites, concentrates, or useformulations; through inadvertent error in these procedures; throughdifferences in the manufacture, source, or purity of starting materialsor ingredients used to carry out the methods; and like considerations.The term “about” also encompasses amounts that differ due to aging of acomposition or formulation with a particular initial concentration ormixture, and amounts that differ due to mixing or processing acomposition or formulation with a particular initial concentration ormixture.

The indefinite article “a” or “an” and its corresponding definitearticle “the” as used herein means at least one, or one or more, unlessspecified otherwise.

Abbreviations, which are well known to one of ordinary skill in the art,may be used (e.g., “h” or “hr” for hour or hours, “g” or “gm” forgram(s), “mL” for milliliters, and “RT” for room temperature, “nm” fornanometers, and like abbreviations).

Specific and preferred values disclosed for components, ingredients,additives, times, temperatures, pressures, and like aspects, and rangesthereof, are for illustration only; they do not exclude other definedvalues or other values within defined ranges. The apparatus, and methodsof the disclosure can include any value or any combination of thevalues, specific values, more specific values, and preferred valuesdescribed herein.

As used herein, a green material is an unfired material comprising amixture of inorganic and/or organic materials. The green material mayinclude various inorganic filler materials, inorganic and/or organicbinder materials, and liquid vehicle. The green material may be dried toremove fluid content (e.g. water). Drying is often accomplished byallowing a part to sit exposed to the ambient atmosphere overnight,however, hot air, forced air, microwave, radio frequency (RF) orinfrared radiation (IR) may be used to augment drying. The drying may beaccomplished in humidity controlled air. Green material may includecold-set cements. The dried green material may be fired to form a porousor non-porous ceramic article.

As used herein, a “super addition” refers to a weight percent of acomponent, such as, for example, an organic binder, liquid vehicle,additive or pore former, based upon and relative to 100 weight percentof the inorganic components of the mixture.

Substrate and filter articles are used in gasoline and diesel, lightduty and heavy duty vehicles for after treatment emission control, andwhich control satisfies environmental regulations. One of the steps inthe production of these substrates and filters is the application of acement-based skin or outer wall on the outer peripheral axial surface ofthe substrates and filters.

The skin on a part, such as a porous ceramic filter article, is theinterface between the part and the surroundings. The skin serves severaladvantageous functions, for example, the skin adds to the aesthetics ofthe part and is valued by customers as an indicator of quality, protectsthe part's functional filter portion from structural degradation such aschipping damage, and other hazards surrounding the part, in manufactureand use, such as in handling and transport of the part, and adds to theisostatic strength of the part, which is a significant performancemetric for modern parts.

FIG. 1A shows a honeycomb body 100 including a plurality of intersectingwalls 110 that form mutually adjoining cell channels 112 extendingaxially between opposing end faces 114, 116. FIG. 1B shows a schematiccross section through the honeycomb body 100 of FIG. 1A. FIG. 1C shows aschematic top view of the honeycomb body 100 of FIG. 1A. “Cell” isgenerally used herein when referring to intersecting walls in crosssection of the honeycomb body and “channel” is generally used whenreferring to a cell extending between the end faces 114, 116. Cell andchannel may be used interchangeably as well as “cell channel”. A“partial cell” or “partial cell channel” 120 when used herein refers toa cell or channel at the outer periphery 118 of a contoured honeycombbody 100 (honeycomb core 104) having a gap 122 in intersecting walls110. The top face 114 refers to the first end face and the bottom face116 refers to the second end face of the honeycomb body 100 positionedin FIG. 1A, otherwise the end faces are not limited by the orientationof the honeycomb body 100. The top face 114 may be an inlet face and thebottom face 116 may be an outlet face of the honeycomb body 100 or thetop face 114 may be an outlet face and the bottom face 116 may be aninlet face of the honeycomb body 100.

Cell density can be between about 100 and 900 cells per square inch(cpsi). Typical cell wall thicknesses can range from about 0.025 mm toabout 1.5 mm (about 1 to 60 mil). For example, honeycomb body 100geometries may be 400 cpsi with a wall thickness of about 8 mil (400/8)or with a wall thickness of about 6 mil (400/6). Other geometriesinclude, for example, 100/17, 200/12, 200/19, 270/19, 600/4, 400/4,600/3, and 900/2. As used herein, honeycomb body 100 is intended toinclude a generally honeycomb structure but is not strictly limited to asquare structure. For example, hexagonal, octagonal, triangular,rectangular or any other suitable cell shape may be used. Also, whilethe cross section of the cellular honeycomb body 100 is circular, it isnot so limited, for example, the cross section can be elliptical,square, rectangular, or other desired shape.

The honeycomb body 100 generally has a honeycomb core 104 having anouter periphery 118 and a skin 124. The skin 124 may be co-extruded orapplied after a contouring operation. FIG. 2 shows a perspective view ofan exemplary embodiment of a honeycomb core 104 after contouring andbefore skinning. The honeycomb core 104 may be green and dried beforecontouring and skinning or may be fired. The walls 110 at the outer mostperiphery 118 of the contoured honeycomb core 100 may form partial cells120 as well as cells 112. The partial cells 120 are generally spacedoutward from the cells 112. However, a cell 112 may be outer most whenwalls 110 forming the cell 112 meet at the outer periphery 118. Theouter most portions of the walls 110 of the partial cells 120 and theouter most corner 126 of some cells 112 form the outer periphery 118 ofthe contoured honeycomb core 104.

Exemplary embodiments of the disclosure relate to ceramic articleshaving a honeycomb core 104 such as shown in FIG. 2, which may be formedof a single monolith or formed of segments cemented together to form amonolith. The honeycomb core 104 includes a plurality of channel walls110 extending from an inlet face 114 to an outlet face 116 defining cellchannels 112 and partial cell channels 120 therebetween, an outerperiphery 118 extending from the inlet face 114 to the outlet face 116,where partial cell channels 120 adjoin the outer periphery 118 of thehoneycomb core 104. A skin 124 is disposed on the outer periphery 118 ofthe honeycomb core 104 such that a majority of the total partial cellchannel volume is open from the inlet face 114 to the outlet face 116 asshown in FIGS. 1A, 1B, and 1C to form a honeycomb body 100. While thisdisclosure relates to after-applied skins, such after-applied skins maybe disposed on co-extruded skins.

In these exemplary embodiments the honeycomb core 104 may be formed froma ceramic material, such as cordierite or in other cases may be made ofother ceramic materials, such as silicon carbide, silicon nitride,aluminum titanate, alumina and/or mullite, or combinations thereof.

The honeycomb body can be formed according to any conventional processsuitable for forming honeycomb monolithic bodies. For example, aplasticized ceramic forming batch composition can be shaped into a greenbody by any known conventional ceramic forming process, such asextrusion, injection molding, slip casting, centrifugal casting,pressure casting, dry pressing and the like. Typically, honeycombstructures are formed by an extrusion process where a ceramic materialis extruded into a green form before the green form is fired to form thefinal ceramic structure. In an exemplary embodiment, the extrusion canbe performed using a hydraulic ram extrusion press, a two stagede-airing single auger extruder or a twin screw mixer with a dieassembly attached to the discharge end. The extruded material can be cutto create honeycomb structures such as filter bodies shaped and sized tomeet the needs of engine manufacturers. The extruded material can behoneycomb segments connected or bonded together to form the honeycombstructures. These extruded green bodies can be any size or shape.

Generally, as a ceramic honeycomb structure is extruded, a solidexternal surface is provided along the length of the structure. Undercertain circumstances, however, it may become necessary to remove theexternal surface. For example, a green extruded honeycomb structure maybe shaped to a desired shape and size by removing the extruded externalsurface. Alternatively, the green honeycomb structure may be fired andthen ground to the desired shape and size by removing the externalextruded surface and any portion of the porous wall structure necessaryto attain the desired shape and size. Shaping can be accomplished by anymeans known in the art, including cutting, sanding or grinding away theouter extruded surface of the honeycomb structure to achieve the desiredshape and size.

Likewise, honeycomb segments may be shaped to a desired shape and sizeby removing the extruded external surface before integrating to thehoneycomb structure. Alternatively, the honeycomb segments may beintegrated to form a honeycomb structure and the formed honeycombstructure shaped to the desired shape and size.

Once the desired shape and size has been attained, a skin material canbe applied to an outer periphery of the sized body to form a newexternal surface, or skin, on the body. Typically, the ends of thehoneycomb body are not covered with the skin material, although certainpassages may be plugged if desired. Once the skin composition has beenapplied to the honeycomb structure, the skin composition can be driedand/or calcined. In some embodiments a cold-set cement composition maybe applied to the honeycomb structure. In some embodiments, thehoneycomb core over which the cement is applied comprises fired ceramicmaterial. In other embodiments, the honeycomb core comprises a greenbody or a calcined body. In some cases, final firing of the calcinedhoneycomb structure can take place during the catalyzation process.

In these exemplary embodiments once the desired shape and size of thehoneycomb core has been attained, a sheet is disposed on the honeycombcore and a skin batch is disposed on the sheet. FIG. 3A is a schematicend view of a honeycomb core 104 having a sheet 130 disposed on theouter periphery 118. The sheet has an inner surface 132 and an outersurface 134. The inner surface 132 is disposed on the outer periphery118 such as by a wrapping operation in which the sheet inner surface 132may overlap the sheet outer surface 134 at an overlap portion 136.Alternatively, the sheet 130 may be in the form of a sleeve with nooverlap portion. When the sheet 130 is in the form of a sleeve, applyingthe sheet 130 to the honeycomb core 104 may include an operation wherethe sheet 130 may slide over an end face 114, 116 of the honeycomb core104 to be disposed on the outer periphery 118.

The sheet 130 can be disposed on the outer most portions of the walls110 of partial cells 120 and outer most corners 126 of cells 112 thatform the outer periphery 118 of the contoured honeycomb core 104. Thesheet 130 provides a barrier to prevent skin batch from filling partialcells 120. FIG. 3B shows a schematic end view of a honeycomb core 104having a sheet 130 disposed on the outer periphery 118 and a layer ofskin batch 140 disposed on the outer surface 134 of the sheet 130. Thelayer of skin batch 140 has an inner surface 142 contacting the outersurface 134 of the sheet 130 and an outer surface 144 forming the outerperiphery of the honeycomb body 100.

The skin batch can be applied to the honeycomb core 104 shrouded in thesheet 130 by a doctor blade operation, by an axial skinning operation,by a spray casting operation, by a tape casting operation, or the like.The sheet 130 prevents the layer of skin batch 140 from filling thepartial cells 120, however, the skin batch may penetrate the sheet 130to contact the outer most portions of the walls 110 of the partial cells120 and the outer most corner 126 of some cells 112 that form the outerperiphery 118 of the contoured honeycomb core 104. In this sense, thesheet 130 may be porous to allow skin batch to contact the honeycombcore walls 110. The skin batch contacting the honeycomb core walls 110bonds the skin batch layer 140 to the honeycomb core 104 when the skinbatch is cured forming the honeycomb body. Curing the skin batch mayinclude sacrificing the sheet 130. For example, the skin batch may befired or calcined to form an outer skin and burning off the sheet 130leaving a portion of the skinned partial cell channels 120 open from theinlet face 114 to the outlet face 116.

The sheet 130 may be wetted, for example, with water, or the sheet 130may comprise a constituent of the skin 124. Wetting the sheet 130 mayfacilitate disposing the sheet 130 on the honeycomb core 104. Wettingand drying the sheet 130 can shrink the sheet 130 to the honeycomb core104 further facilitating subsequent skinning operations. The sheet 103impregnated with one or more constituents of the skin 124 or skin layer140 may enhance bonding of the skin 124 to the honeycomb core 104 whilepreventing defects such as cracks and the like. One such constituent maybe an inorganic binder such as colloidal silica, colloidal alumina, orthe like, and combinations thereof.

In exemplary embodiments the sheet 130 can be at least one of a porouswoven sheet, a porous non-woven sheet, a non-porous woven sheet, and anon-porous non-woven sheet. The sheet is not particularly limited andcan include, natural and synthetic materials, the sheet may be adhesivebacked or non-adhesive backed. Examples of sheet materials include glassfiber tape, glass fiber cloth, cellulose fiber, polymers such aspolyethelene fiber cloth, nylon fiber cloth, and polyester fiber cloth,other examples of sheet material include carbon fiber fabric, paper,paper tissue, such as Kimwipe®, mesh, natural fiber cloth, such ascotton, silk, hemp, or linen, and the like. Porosity can be in a rangefrom nanometer scale to millimeter scale. The sheet thickness can be ina similar range, for example, from microns to millimeters. For example,the sheet thickness can be about 50 to 1500 μm and the pore openings canbe from about 1 μm to about 1500 μm. When the sheet 130 is porous,constituents of the skin batch can penetrate the sheet 130 and bond theskin layer 140 to the honeycomb core 104. When the sheet 130 isnon-porous, constituents of the skin layer may penetrate the sheet 130during calcining or curing to allow the skin material layer 140 to bondto the honeycomb core 104 outer periphery 118. When the sheet 130 isnon-porous, the sheet 130 may react during calcining, firing, or curingto allow the skin material layer 140 to bond to the honeycomb core 104outer periphery 118.

As another non-limiting method of characterizing sheet parameters, sheetdensity may be used. For example, the sheet can have a density fromabout 0.1 oz/sq yd to about 50 oz/sq yd. For example, the sheet materialmay be about 0.7 oz/sq yd, about 1.5 oz/sq yd, about 2 oz/sq yd, about2.7 oz/sq yd, or even about 3.2 oz/sq yd.

In an alternative exemplary embodiment, the skin batch layer 140 may bedisposed on the sheet 130 prior to the operation of disposing the sheet130 on the honeycomb core 104. In such an instance, the sheet 130 havingthe batch layer 140 disposed on the outer surface 134 can be applied tothe honeycomb core 104 as described above.

The sheet 130 may have a layer of skin batch disposed on the sheet innersurface 132 prior to disposing the sheet 130 on the outer periphery 118.The sheet 130 prevents the layer of skin batch disposed on the innersurface 132 from filling the partial cells 120. The skin batch on theinner surface 132 contacting the honeycomb core walls 110 bonds the skinbatch layer 140 to the honeycomb core 104 when the skin batch is curedforming the honeycomb body 100. In this exemplary embodiment, the sheet130 may be sacrificed or transformed during curing, firing, orcalcination to form the outer skin 124. When skin batch cement isdisposed on the inner surface 132 and the outer surface 134, the batchcement can comprise the same composition on the inside and outside ofthe sheet 130 or batch cements can comprise different compositions onthe inside and outside of the sheet. For example, for the skin 124 tomatch desired physical properties (elastic modulus (EMOD), coefficientof thermal expansion (CTE), modulus of rupture (MOR), and the like) ofthe honeycomb core 104, a first composition can be applied to the innersurface 132 and for desired physical properties of the outer surface ofthe skin 124 such as different MOR, EMOD, CTE, a second composition canbe applied to the outer surface 134.

In an alternative embodiment, a filling material 138 can be disposed onthe outer periphery 118 of the honeycomb core 104 to fill the partialcells 120 prior to applying a skin batch material (FIG. 3C). The fillingmaterial 138 may be applied in the partial cells 120 and cleaned away toexpose the outer most portions of the walls 110 of the partial cells 120and the outer most corner 126 of some cells 112 that form the outerperiphery 118 of the contoured honeycomb core 104. In this way, when theskin batch is applied to the honeycomb structure 104 comprising thefilling material 138, the skin batch may contact the outer most portionsof the walls 110 of the partial cells 120 and the outer most corner 126of some cells 112 that form the outer periphery 118 of the contouredhoneycomb core 104. The skin batch contacting the honeycomb core walls110 bonds the skin batch layer to the honeycomb core 104 when the skinbatch is cured forming the honeycomb body 100. Curing the skin batch mayinclude sacrificing the filling material 138. For example, the skinbatch may be fired or calcined to form an outer skin 124 and burning offthe filling material 138 leaving a portion of the skinned partial cellchannels 120 open from the inlet face 114 to the outlet face 116.

The filling material 138 can comprise wax, naphthalene, and the like.The filling material 138 can be a paste at room temperature andvolatilize at high temperature such as at drying, curing, calcining, orfiring temperatures.

Once the skin material has been applied to the sheet 130 or the fillingmaterial 138 on the honeycomb structure in a manner as described herein,the skin material can be optionally dried and/or fired. The optionaldrying step can comprise first heating the skin material in a humiditycontrolled atmosphere at a temperature and for a period of timesufficient to at least substantially remove any liquid vehicle that maybe present in the skin material. As used herein, at least substantiallyremoving any liquid vehicle includes the removal of at least 95%, atleast 98%, at least 99%, or even at least 99.9% of the liquid vehiclepresent in the skin material prior to firing. Exemplary and non-limitingdrying conditions suitable for removing the liquid vehicle includeheating the skin material at a temperature of at least 50° C., at least60° C., at least 70° C., at least 80° C., at least 90° C., at least 100°C., at least 110° C., at least 120° C., at least 130° C., at least 140°C., at least 150° C., at least 160° C., at least 170° C., at least 180°C., at least 190° C., or even at least 200° C. In one embodiment, theconditions effective to at least substantially remove the liquid vehiclecomprise heating the skin material in a humidity controlled atmosphere,such as air, at a temperature in the range of from 60° C. to 120° C.Further, the heating can be provided by any conventionally known method,including for example, hot air drying, RF and/or microwave drying in ahumidity controlled atmosphere.

The optional firing step can include conditions suitable for convertingthe skin material to a primary crystalline phase ceramic compositioninclude heating the honeycomb with applied skin material to a peaktemperature of greater than 800° C., 900° C., and even greater than1000° C. A ramp rate of about 120° C./hr during heating may be used,followed by a hold at the peak temperature for a temperature of about 3hours, followed by cooling at about 240° C./hr.

Skin material disclosed herein can include those that set at atemperature of less than 200° C., such as a temperature of less than100° C., and further such as a temperature of less than 50° C.,including cement material that can be used in skinning processesemploying “cold set” skins. In cold set skinning, only drying of theskinning mixture is required to form a seal of the channel walls of thehoneycombs. When a cold set skinning process is employed, heating of theskinned honeycombs to temperatures in the 35-110° C. range can be usefulto accelerate drying. In some cold set skinning processes, it isanticipated that final skin consolidation, including the removal ofresidual temporary binder bi-products such as the sheet 130 andstrengthening of the seals, can occur in the course of subsequentprocessing steps (e.g., in the course of catalyzation or canning) orduring first use (e.g., in an exhaust system).

For example, exemplary compositions in which cold set skinning may beemployed include those comprising a refractory filler that comprises atleast one inorganic powder, such as at least one of aluminum titanate,cordierite, fused silica, mullite, and alumina, the inorganic powderhaving a bimodal or mono sized median particle size (D₅₀) of from 15 to50 microns, such as from 30 to 40 microns for mono sized andadditionally a median particle size in a range from about 150 microns toabout 300 microns, such as from about 150 microns to about 250 micronsfor the second particle size in bimodal size compositions, and a gelledinorganic binder, such as gelled colloidal silica. At least one gellingagent, such as at least one of hydrochloric acid, sulfuric acid, nitricacid, citric acid, and acetic acid, ammonium hydroxide, sodiumhydroxide, and triethanol amine (hereinafter “TEA”) may be added eitherbefore (e.g., as a pre-mix with the gelled inorganic binder) or duringbatching in order to gel the inorganic binder. Alternatively anon-gelled composition may be used. Such compositions can provide skinsthat set in a porous ceramic honeycomb body (and be thereby permanentlysealed to the channel walls) at a temperature of less than 200° C., suchas less than 100° C., and further such as less than 50° C., includingabout 25° C. Further non-limiting exemplary embodiments of cementcompositions used for skinning are discussed below.

Skin compositions are described in U.S. Provisional Patent ApplicationNo. 61/602,883 and U.S. patent application Ser. No. 13/302,262, thecontents of which are incorporated herein by reference in theirentirety. According to exemplary embodiments the skin composition may bea single glass powder composition including a cement comprising a glasspowder as a low thermal expansion filler material, a binder and asolvent or vehicle for carrying the solid constituents of theglass-based cement. The glass of the glass powder filler material may bean amorphous fused silica (SiO₂), ground cordierite, AT grog, or silicasoot. The glass powder filler material can have a median particle size(D50) between 10 and 20 μm, with a minimum particle size between 7 μmand 75 μm and a maximum particle size between 50 μm and 70 μm. Particlesize determined as a mass-based equivalent spherical diameter. The glasspowder filler material may comprise, for example, from 60-80 wt. % ofthe total inorganic components of the cement. Suitable silica powderfiller materials are available, for example, under the trade nameTeco-Sil, available from CE Minerals of Tennessee Electro MineralsIncorporated, Tennessee, USA. All particle size measurements herein weremade with a Microtrac Inc. particle size analyzer, unless otherwiseindicated.

According to exemplary embodiments the skin composition may include anamorphous glass-based cement, the cement formed from a dual glass powdercomposition comprising a first (fine) glass powder as a low thermalexpansion filler material, a second (coarse) glass powder as a lowthermal expansion filler material, a binder and a solvent or vehicle forcarrying the solid constituents of the glass-based cement. The glassesof both the first glass powder filler material and the second glasspowder filler material may be amorphous fused silica having particlesizes greater than about 1 μm. The distribution of glass powder fillermaterial particle size can be multimodal in that a distribution of theglass powder filler material with particle sizes greater than about 1 μmexhibits multiple modes (local maximums) of particle sizes. In oneembodiment, the amorphous glass-based cement comprises a bimodalparticle size distribution of amorphous glass particles with a particlesize greater than about 1 μm. The glass based cement may include a firstglass powder filler material wherein a median (D50) particle size of thefirst glass powder filler material can be in a range from about 10 toabout 50 μm, from about 15 μm to about 50 μm, from about 20 μm to about45 μm or from about 30 μm to about 45 μm, with a D10 in a range fromabout 1 μm to about 10 μm and D90 in a range from about 25 μm to about125 μm. A median (D50) particle size of the second glass powder fillermaterial can be in a range from about 150 μm to about 300 μm, in a rangefrom about 150 μm to about 250 μm, in a range from about 170 μm to about230 μm, in a range from about 180 μm to about 220 μm, with D10 in arange from about 100 μm to about 150 μm, and D90 in a range from about250 μm to about 350 μm. Particle sizes are determined as a mass-basedequivalent spherical diameter. As used herein, the term D50 representsthe median of the distribution of particle sizes, D10 represents theparticle size in microns for which 10% of the distribution are smallerthan the particle size, and D90 represents the particle size in micronsfor which 90% of the distribution are smaller than the particle size.The dual glass based cement may contain, for example, an amount of thefirst glass powder filler material in a range from about 20 to about 60wt. % of the total weight of the inorganic solid components of thecement, in a range from about 25 wt. % to about 50 wt. %, in a rangefrom about 25 wt. % to about 40 wt. %, or in a range from about 25 wt. %to about 35 wt. %. The glass based cement may contain, for example, anamount of the second glass powder filler material in a range from about10 wt. % to about 40 wt. % of the total weight of the inorganic solidcomponents of the cement, in a range from about 15 wt. % to about 40 wt.%, in a range from about 20 wt. % to about 35 wt. %.

In one exemplary embodiment, D50 of the first glass powder fillermaterial may be in a range from about 34 μm to about 40 μm, and a medianparticle size of the second glass powder filler material is in a rangefrom about 190 μm to about 280 μm. In one example, the first glasspowder filler material has a D10 of about 6.0 μm, a D50 of about 34.9 μmand a D90 of about 99 μm. In another example, the first glass powderfiller material has a D10 of about 6.7 μm, a D50 of about 39.8 μm, and aD90 of about 110.9 μm. In still another example, the first glass powderhas a D10 of about 2.7 μm, a D50 of about 13.8 μm and a D90 of about37.8 μm, and as yet another example, the first glass powder fillermaterial has a D10 of about 2.8 μm, a D50 of about 17.2 μm and a D90 ofabout 47.9 μm.

The ratio of the second glass powder filler material to the first glasspowder filler material may be in a range from about 1:4 to about 1:1,such as about 1:3.5 to about 1:1, from about 1:3 to about 1:1, fromabout 1:2.5 to about 1:1, from about 1.2 to about 1:1 or from about1:1.5 to about 1:1. In an exemplary embodiment, the ratio of the secondglass powder filler material to the first glass powder filler materialis 1:1.

To provide the cement compositions of the present disclosure, theinorganic powders comprising any of the above inorganic powders and anyoptional inorganic additive components can be mixed together with asuitable organic and/or inorganic binder material. The organic bindermaterial may comprise one or more organic materials, such as a celluloseether, methylcellulose, ethylcellulose, polyvinyl alcohol, polyethyleneoxide and the like, or in some embodiments a gum-like material such asActigum®, xanthan gum or latex. For example, A4 Methocel is a suitableorganic binder. Methocel A4 is a water-soluble methyl cellulose polymerbinder available from Dow Chemical. A suitable inorganic binder maycomprise colloidal silica or alumina comprising nanometer-scale silicaor alumina particles suspended in a suitable liquid, such as water. Theinorganic binder material can be present in the cement composition in anamount less than about 10% of the total weight of inorganic solidspresent in the cement, and in some exemplary embodiments inorganicbinders are present in an amount equal to or less than about 5 wt. %,and in certain other exemplary embodiments in a range from about 2 wt. %to about 4 wt. % taking into account the fluid portion of the organicbinder (wherein the weight contribution of the fluid portion isremoved). A suitable colloidal silica binder material is Ludox HS40produced by W.R. Grace. Typical colloidal binder materials may compriseapproximately 40% by weight solid material as a suspension in adeionized water vehicle.

In some exemplary embodiments, the single and dual glass powder cementsdescribed supra may also include an inorganic fibrous reinforcingmaterial. For example, aluminosilicate fibers may be added to the cementmixture to strengthen the honeycomb structure after application of theskin. For example, the cement may include an inorganic fibrous materialfrom about 25 to about 50 wt. % of the total weight of the inorganicsolid components of the cement, from about 30 to about 50 wt. %, and insome embodiments from about 35 to about 45 wt. % of the total weight ofthe inorganic solid components of the cement. In certain otherembodiments, fibrous inorganic reinforcing materials may be present inan amount from about 36 wt. % to about 43 wt. % as a percentage of thetotal weight of the inorganic solids of the cement composition. Asuitable inorganic fibrous reinforcing material is Fiberfrax QF 180,available from Unifrax, however, any high aspect ratio refractoryparticulate could be used.

Typically, the liquid vehicle or solvent for providing a flowable orpaste-like consistency has included water, such as deionized (DI) water,although other materials may be used. The liquid vehicle content may bepresent as a super addition in an amount equal to or less than about 30wt. % of the inorganic components of the cement mixture, can be in arange from about 10 wt. % to about 25 wt. % of the inorganic componentsof the cement mixture. However, the liquid vehicle is typically adjustedto obtain a viscosity suitable to make the cement easy to apply.

In some embodiments the cement may optionally further contain organicmodifiers, such as adhesion promoters for enhancing adhesion between thecement and the honeycomb body. For example, Michem 4983 has been foundsuitable for this purpose.

In certain exemplary embodiments, the cement mixture sets at atemperature of less than 1000° C., such as a temperature of less than800° C., and further such as a temperature of less than 600° C., and yetfurther such as a temperature of less than 400° C., and still yetfurther such as a temperature of less than 200° C. In certain exemplaryembodiments, the cement mixture is capable of setting at roomtemperature (i.e., at about 23° C.).

Cement compositions described herein can exhibit viscosities well suitedfor forming an external skin over a sheet on a honeycomb core. Forexample, compositions according to the embodiments herein can have aninfinite shear viscosity equal to or less than about 12 Pascal-seconds(Pa·s.), equal to or less than about 5 Pa·s., or equal to or less thanabout 4 Pa·s. For a shear rate of 10 s⁻¹, the shear viscosity may, forexample, be equal to or less than about 400 Pa·s, equal to or less thanabout 350 Pa·s or less than or equal to about 300 Pa·s. Viscosity wasmeasured using a parallel plate viscometer.

Calcining of cement compositions disclosed herein can be conducted in abox furnace with a linear ramp to 600° C. in 3 hours, followed by a holdfor 3 hours at 600° C., then followed by a ramp down to room temperatureover a time period of 3 hours. In commercial use, the ceramic articlecan be wash coated with catalyst followed by a heat treatment to removeorganic materials. The ceramic article can also be canned with a matmaterial that may also require heat treatment to remove organicmaterials. The calcining process simulates service conditionsexperienced by the ceramic article.

The composition of the skin cement is not particularly limited and caninclude, for example, a skin cement of single glass powder compositions,dual glass powder compositions, single glass powder with fibrousreinforcing material compositions, dual glass powder with fibrousreinforcing material compositions, inorganic filler and crystallineinorganic fibrous material compositions, and dual glass powder andcrystalline inorganic fibrous material compositions.

EXAMPLES

Exemplary embodiments of the disclosure are further described below withrespect to certain exemplary and specific embodiments thereof, which areillustrative only and not intended to be limiting. In accordance withsome of the embodiments, a 2 in (5 cm) diameter cordierite honeycombcore having 200 cpsi and 12 mil wall (200/12) geometry was prepared. The2 in (5 cm) honeycomb core was contoured from a 5.7 in (14.5 cm)×6 in(15.3 cm) part. The cordierite honeycomb core is shown in FIG. 4.Partial channels are visible at the outer periphery having an opening orgap as a result of the contouring.

The chemical composition of the skin cement used in the examples isgiven in Table 1

TABLE 1 Skin Material Composition Grams Coarse fused silica 50 Finefused silica 50 Fiberfrax ® QF 180 54 Methocel ™ 1.1 Colloidal Silica 13Water sufficient for viscosity consistency

Comparative Example

FIG. 5 shows a photograph of a 2 in (5 cm) honeycomb core contoured froma 5.7 in (14.5 cm)×6 in (15.3 cm) part as in FIG. 4 having a skinapplied according to a comparative sample. The skinning process in thecomparative process, by not using a sheet, fills nearly all of thepartial cells. Thus, reducing the open frontal area of the honeycombbody. The blocking of the partial cells can adversely affect pressuredrop performance.

Exemplary Embodiments

FIG. 6A shows a photograph of a 2 in (5 cm) honeycomb core contouredfrom a 5.7 in (14.5 cm)×6 in (15.3 cm) part as in FIG. 4 having a sheetapplied according to exemplary embodiments of the disclosure. The sheetcomprises a colloidal alumina slurry treated filter cloth. The filtercloth can prevent skin cement materials entering into the partial cellsand the colloidal alumina slurry can act as a binding material of skincement paste on the honeycomb core to form a honeycomb body. The filtercloth comprises a porous material.

FIG. 6B is a photograph of the 2 in (5 cm) honeycomb core contoured froma 5.7 in (14.5 cm)×6 in (15.3 cm) part of FIG. 6A with applied skincement material on top of wrapped filter cloth and after drying at 100°C. for 120 minutes. The skin cement paste adhered well to the filtercloth. FIG. 6C shows the exemplary sample of FIG. 6B after firing at550° C. for 60 minutes. The wrapped filter cloth was burned out and theskin cement adhered well to the honeycomb core. FIG. 6D shows theexemplary sample of FIG. 6C after trimming the front face to illustratethe preservation of partial cell channels after skin was applied.

FIG. 7A is a photograph of the honeycomb body of FIG. 6C comprising askin on an outer periphery not filling partial cells thereof accordingto exemplary embodiments of the disclosure. FIG. 7B is a highermagnification photograph of a honeycomb body comprising a skin on anouter periphery not filling partial cells shown in FIG. 7A.

FIG. 8 is a photograph of sheets of various composition, mesh size, andthicknesses according to exemplary embodiments of the disclosure used inskinning methods according to exemplary embodiments of the disclosure.Example “AA” is a glass fiber screen of small strand spaced about 1020to 1100 μm having a thickness of about 360 μm. Example “BB” is a glassfiber screen of medium strand spaced about 920 to 1020 μm having athickness of about 550 μm. Example “CC” is a glass fiber cloth having athickness of about 190-200 μm and a pore opening size of about 190-335μm. Example “DD” is a nylon fiber cloth of large hex openings about 3150μm and having a thickness of about 80 μm. Example “EE” is a nylon fibercloth of small hex openings about 544 μm and having a thickness of about180 μm. Example “FF” is a cotton fiber cloth having a thickness of about250 μm to about 275 μm and Example “GG” is a polyester cloth wipe havinga thickness of about 450-500 μm. These thickness measurements wereconducted by optical microscope micrometer.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosure. Thus, itis intended that the appended claims cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

The invention claimed is:
 1. A method of forming a honeycomb body, comprising: disposing a sheet on an outer peripheral surface of a honeycomb core having gaps in intersecting walls, wherein the outer peripheral surface extends from a first end face to a second end face of the honeycomb core; disposing skin batch on the sheet, wherein the sheet provides a barrier to prevent the skin batch from filling a plurality of peripheral partial cell channels; and curing, firing, or calcining the skin batch to form and bond a cured skin to the honeycomb core to form the honeycomb body, wherein the cured skin forms an outer wall closing the gaps in the intersecting walls of the plurality of peripheral partial cell channels while leaving the plurality of peripheral partial cell channels open from the first end face to the second end face.
 2. The method of claim 1, wherein the cured skin comprises at least a portion or constituent of the sheet.
 3. The method of claim 1, wherein disposing the skin batch on the sheet comprises disposing the sheet on the outer peripheral surface of the honeycomb core prior to disposing the skin batch on the sheet.
 4. The method of claim 1, wherein disposing the skin batch on the sheet comprises disposing the skin batch on the sheet prior to disposing the sheet on the outer peripheral surface of the honeycomb core.
 5. The method of claim 1, further comprising firing and contouring the honeycomb core prior to disposing the sheet on the outer peripheral surface.
 6. The method of claim 1, wherein the sheet no more than partially fills the partial cell channels.
 7. The method of claim 1, wherein the sheet is impregnated with a constituent of the cured skin.
 8. The method of claim 1, wherein the sheet is impregnated with colloidal alumina.
 9. The method of claim 1, wherein the sheet is at least one of a porous woven sheet, a porous non-woven sheet, a non-porous woven sheet, and a non-porous non-woven sheet.
 10. The method of claim 1, wherein disposing the sheet on an outer peripheral surface of the honeycomb core comprises wrapping the sheet around the periphery.
 11. The method of claim 10, wherein the sheet comprises a first edge and a second edge opposite the first edge and wrapping the sheet around the periphery comprises disposing the first edge in a direction from the first end face to the second end face, disposing a surface of the sheet on the outer periphery progressively around the honeycomb core, and disposing the surface overlapping a portion of the sheet at the first edge so that the second edge is disposed on the sheet.
 12. The method of claim 10, wherein disposing the sheet on the outer peripheral surface of the honeycomb core, comprises at least one of the sheet extends beyond at least one of the first end face and the second end face, the sheet does not extend to at least one of the first and second end faces, and the sheet extends flush to at least one of the first and second end faces.
 13. The method of claim 1, wherein disposing the sheet on an outer peripheral surface of the honeycomb core comprises sliding the sheet over at least one of the first end face and the second end face wherein the sheet comprises a sleeve.
 14. The method of claim 13, wherein disposing the sheet on the outer peripheral surface of the honeycomb core, comprises at least one of the sheet extends beyond at least one of the first end face and the second end face, the sheet does not extend to at least one of the first and second end faces, and the sheet extends flush to at least one of the first and second end faces.
 15. The method of claim 1, wherein disposing the skin batch on the sheet comprises at least one of doctor blade skinning and axial skinning.
 16. The method of forming a honeycomb body of claim 1, comprising disposing skin batch on an inner surface of the sheet.
 17. The method of forming a honeycomb body of claim 1, wherein the sheet is porous.
 18. A method of forming a honeycomb body, comprising: disposing a sheet on an outer peripheral surface of a honeycomb core, wherein the outer peripheral surface extends from a first end face to a second end face of the honeycomb core; shrinking the sheet on the outer peripheral surface of the honeycomb core; disposing skin batch on the sheet; and curing the skin batch to form a cured skin and to bond the cured skin to the honeycomb core to form the honeycomb body, wherein the cured skin forms an outer wall of a plurality of peripheral partial cell channels while leaving the plurality of peripheral partial cell channels open from the first end face to the second end face.
 19. A method of forming a honeycomb body, comprising: providing a honeycomb core including channel walls and cells, wherein outermost portions of the channel walls and outer most corners of the cells form partial cell channels including gaps adjoining an outer periphery of the honeycomb core; disposing an inner surface of a sheet on the outer periphery of the honeycomb core, wherein the outer periphery extends from a first end face to a second end face of the honeycomb core and the sheet is disposed on the outermost portions of the channel walls and the outer most corners of the cells of the honeycomb core; disposing skin batch on an outer surface of the sheet wherein the sheet prevents the skin batch from filling the partial cell channels; and curing, firing, or calcining the skin batch to form and bond a cured skin to the honeycomb core to form the honeycomb body, wherein the cured skin forms an outer wall closing the gaps and leaving the partial cell channels unfilled from the first end face to the second end face.
 20. A method of forming a honeycomb body, comprising: disposing a sheet on an outer peripheral surface of a honeycomb core having gaps in intersecting walls, wherein the outer peripheral surface extends from a first end face to a second end face of the honeycomb core; disposing skin batch on the sheet; and curing, firing, or calcining the skin batch to form and bond a cured skin to the honeycomb core to form the honeycomb body, wherein the curing, firing, or calcining of the skin batch sacrifices the sheet; wherein the cured skin forms an outer wall closing the gaps in the intersecting walls of a plurality of peripheral partial cell channels while leaving the plurality of peripheral partial cell channels open from the first end face to the second end face.
 21. A method of forming a honeycomb body, comprising: disposing a sheet on an outer peripheral surface of a honeycomb core having gaps in intersecting walls, wherein the outer peripheral surface extends from a first end face to a second end face of the honeycomb core; disposing skin batch on the sheet; and curing, firing, or calcining the skin batch to form and bond a cured skin to the honeycomb core to form the honeycomb body, wherein the curing, firing, or calcining comprises burning off the sheet; wherein the cured skin forms an outer wall closing the gaps in the intersecting walls of a plurality of peripheral partial cell channels while leaving the plurality of peripheral partial cell channels open from the first end face to the second end face. 